[doc] run playbooks in two separate commands
    
    Unfortunatelly, `rbac-playbook` doesn't accept more than one playbook
    at the time, so we need to run upgrade and provision playbooks in two
    separate commands. I've submitted an issue
    https://bitbucket.org/tflink/ansible_utils/issues/4/
    requesting `rbac-playbook` to optionally accpet more playbooks.
    Once the feature is available on batcave01, we can revert this
    commit.